Device for the multi-channel measurement of weak variable magnetic fields with squids and superconducting gradiometers arranged on a common substrate

Abstract

An improved device for the multi-channel measurement of weak variable magnetic fields with fields strengths below 10 -10 T, having in each channel a superconducting quantum interference device (SQUID), a gradiometer consisting of superconducting coils and superconducting elements between the quantum interference device and the gradiometer, and a coupling transformer and connecting leads. In addition, the device includes electronic equipment for the evaluation, processing and presentation of the information obtained at the quantum interference elements. In order to use this measurement device to obtain spatial field distributions, particularly those of biomagnetic fields, during reasonable measuring times, with a substantial coherence among the field data, the invention provides for a rigid substrate on which direct-current quantum interference devices with associated planar-designed gradiometer coils and the superconducting connecting elements are arranged, and in which case the coils and the connecting elements are thin-film structures on at least one level.

I claim: 
     
       1. In a multi-channel device for the multi-channel measurement of weak variable magnetic fields with field strenghts below 10 -10  T wherein each channel includes a superconducting quantum interference device (SQUID), a gradiometer of predetermined order having superconducting coils and superconducting connecting elements from the quantum interference device to the gradiometer, said superconducting connecting elements include an associated coupling transformer and connecting leads, and the multi-channel device includes electronic equipment connected to the superconducting quantum interference devices for the evaluation, processing and presentation of information obtained at the quantum interference devices, the improvement comprising a common rigid substrate having mounted thereon all of said direct current superconducting quantum interference devices, planar-designed gradiometer coils comprising an array of detection coils and an array of compensation coils, at least one of said detection coils and at least one of said compensation coils being assoicated with a respective one of said quantum interference devices and said superconducting connecting elements, wherein said gradiometer coils and said superconducting connecting elements are arranged as thin-film structures on one or more levels of said common rigid substrate. 
     
     
       2. The measurement device of claim 1, wherein said direct-current superconducting quantum interference devices are deposited on a common carrier chip and said common carrier chip is securely fastened to said rigid substrate. 
     
     
       3. The measurement device of claim 2, wherein said gradiometer coils are of the 1st or a higher order, wherein said rigid substrate includes a single carrying part for said gradiometer coils, said connecting elements and said carrier chip of the direct-current superconducting quantum interference devices. 
     
     
       4. The measurement device of claim 1, wherein all of said gradiometer coils are deposited on a common face of said rigid substrate next to one another. 
     
     
       5. The measurement device of claim 1, wherein said rigid substrate is composed of a plurality of parts. 
     
     
       6. The measurement device of claim 5, wherein said gradiometer coils are of the second order, wherein said rigid substrate includes two carrying parts, each of said parts being equipped with a gradiometer of the first order. 
     
     
       7. The measurement device of claim 5, wherein said rigid substrate comprises quartz or silicon parts. 
     
     
       8. The measurement device of claim 1, wherein said detection coils have a different number of windings and different surface areas as compared with said associated compensation coils. 
     
     
       9. The measurement device of claim 1, wherein said detection coils and said compensation coils are arranged on different parallel faces of said rigid substrate. 
     
     
       10. The measurement device of claim 9, wherein said direct-current superconducting quantum interference devices are deposited on a face of said rigid substrate, said face being in a plane other than that of said faces on which said gradiometer coils are deposited. 
     
     
       11. The measurement device of claim 9, wherein said connections between said gradiometer coils are located on said parallel faces, and are formed by thin-film conductors running between edges of said faces. 
     
     
       12. The measurement device of claim 9, wherein said connections between said gradiometer coils and said direct-current superconducting quantum interference devices are formed by thin-film conductors running between said edges of said faces carrying these parts. 
     
     
       13. The measurement device of claim 12, wherein said connection of said superconducting conductor elements to said edges is formed by soldering joints with superconducting material in grooves. 
     
     
       14. The measurement device of claim 13, wherein said edges that include said grooves are beveled. 
     
     
       15. The measurement device of claim 2, wherein said carrying chip is fastened indirectly to said rigid substrate by means of an intermediate carrier. 
     
     
       16. The measurement device of claim 15, wherein said intermediate carrier has slits in the area of said superconducting conductor terminals.